Pressure-baking and expanding a starch-containing raw food material into puffed crackers, cakes, mini-cakes and similar snacks, which is usually carried out between the heated dies of a closable mould, has now become a standard technology in the field of manufacturing health-promoting nutrition products of low fat content with appropriate amounts of protein and carbohydrates. Production processes and apparatuses for puffed crackers are disclosed in numerous patent publications such as e.g. U.S. Pat. No. 4,328,741, U.S. Pat. No. 4,667,588, U.S. Pat. No. 4,734,289, U.S. Pat. No. 4,888,180, U.S. Pat. No. 5,102,677, U.S. Pat. No. 5,376,395, U.S. Pat. No. 5,467,693, U.S. Pat. No. 5,562,021, U.S. Pat. No. 5,755,152, EP-A-0367031, WO-A-88/00797, EP-A-0499301, EP-A-1025764 etc. Each one of said documents teaches specific apparatus designs and/or process variations for improving particular aspects of puffed cracker manufacture.
In addition there have been made various proposals to render the taste, texture and shape of the puffed crackers more amenable to consumer preferences. However, conventional technology often fails to produce a consistent product at acceptable economics and known machinery is mostly not capable of producing crackers of widely varying expansion degree and base shapes or textures differing too much.
The instant inventor, having examined the different ways of prior art cracker processing, came to the conclusion that the existing methods and devices of commercial importance still had room for improvement with respect to control and effectiveness of the baking-expansion cycle, in particular its adjustment and fine-tuning according to required product type. The aim of better expansion control is generally the provision of a more reliable production method in terms of cracker quality, yield and machine productivity. However, more recent and special cracker products are deemed to involve more closely controlled and adaptable baking-expansion cycles, which cannot be performed with standard technology or at least not in optimal conditions. Therefore, there is a need to provide production methods and apparatuses having the ability and the flexibility to produce, in a consistent way, quite different requirements of puffed crackers in terms of shape, density and cereal or starch base compositions. In this way special consumer preferences regarding desired combinations of cracker properties (including crispness, taste, density, shape stability, texture etc.) could be developed and incorporated into different particular cracker qualities.
To achieve this goal there is apparently a need for further apparatus improvements and adequate process innovations, which up to now have not addressed or suggested in the prior art.
In this connection patent U.S. Pat. No. 5,102,677 discloses an improved drive system comprising a toggle mechanism actuated by a hydraulic jack having its driven shaft arranged in a nearly horizontal position to the side of the toggle member. Said document also describes a three-part mould with fixed upper die and moveable ring die.
Document U.S. Pat. No. 5,376,395 to Pels is directed to a baking-expansion system using a fixed mould ring receiving at opposite mould entries a moveable upper die and a moveable lower die, thereby allowing a pressure relief of the mould cavity as a pre-expansion step. The dies are arranged in a vertical alignment of their support axis and driven shaft without specifying the drive system.
Document EP-A-1025764 to Quaker describes a process for manufacturing low-density crackers making use of standard pressure-baking technology. The Quaker document shows vertical alignment of support axis and driven shaft for the respective upper and lower dies, which is usual in apparatuses with fixed central mould and pneumatically driven upper and lower dies.
The prior art, however, is silent on (concrete) hydraulic drives for apparatuses as disclosed in the above mentioned Pels and Quaker documents. Indeed, “direct” hydraulic drives were commonly considered to be inadequate for two main reasons: on the one hand an intrinsic risk of hydraulic oil spoilage and possible oil contaminations, which is totally unacceptable in the food industry, and on the other hand the fact and conviction that hydraulic cylinder are normally too slow for accommodating the very high (explosion-like) expansion speeds in puffing cereal materials.
The present invention circumvents the possible oil contamination problem by providing only one hydraulic drive and arranging it below the granular-food containing mould cavity.
The object of the present invention is to avoid the drawbacks of prior art devices and processes in producing expanded crackers. A further object of the invention is to improve productivity and flexibility of existing cracker manufacturing technology and to render the machinery less cumbersome and more reliable.
These and other objects are achieved by the present invention in proposing the combination of a three-part mould, which is part of a previous development by the present inventor, and of a novel apparatus drive and process control concept, designed for being capable of providing a direct drive actuation and enabling a quick expansion response, which expansion is moreover adjustable to a precise variable extent
This concept allows the economic production of a broader range of “customized” puffed snack products, while retaining for each product the required consistency in shape and quality together with the incorporated desired special properties.
Furthermore, the machine operation remains simple whilst the compact apparatus itself allows flexibility and yet mass production of different kinds of expanded products, and this in circumstances of high technical reliability and economic competitiveness.